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Biology - notes
General Biology I (BIOL101 )
Harrisburg Area Community College
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Chapter 23 Notes The Evolution of Populations Evolution of Populations Organisms do NOT evolve, populations do. However, organisms are affected natural selection. The evolutionary impact of natural selection on individuals is only apparent in the changes of a population of organisms over time Example: beak lengths do not evolve in the individual to be longer to make up for a different size of food, but the individuals with longer beaks survive to reproduce and pass on the trait of the longer beak to their offspring and the next generation has a larger percentage of that trait. Microevolution change in allele frequencies in a population over generations Caused three main mechanisms: 1. Natural selection 2. Genetic drift change events that alter allele frequency 3. Genes flow transfer of alleles between populations Genetic Variation and Evolution Variation in heritable traits was a prerequisite for evolution Darwin did not know the mechanism to explain this though Genetic Variation Differences among individuals in the composition of their genes of other DNA segments Examples: facial features, height, voice, blood type Genotype variation, because phenotype can be altered the environment and personal actions Example: body builders Only the genetically determined part of phenotypic variation can have evolutionary consequences WITHOUT GENETIC VARIATION, EVOLUTION COULD NOT OCCUR Variation Within a Population Discrete Characters determined single gene locus with different alleles that produce distinct phenotypes Example: pea plants Qualitative Characters variation on a continuum within a population Result from the influence of two or more genes on a single phenotypic character Measure genetic variation: At whole gene level: Gene Variability Quantified as the average heterozygosity (average percentage of loci that are heterozygous) for fruit small percentage, but provides enough material for natural selection to work Chapter 23 Notes The Evolution of Populations Evolution of Populations Organisms do NOT evolve, populations do. However, organisms are affected natural selection. The evolutionary impact of natural selection on individuals is only apparent in the changes of a population of organisms over time Example: beak lengths do not evolve in the individual to be longer to make up for a different size of food, but the individuals with longer beaks survive to reproduce and pass on the trait of the longer beak to their offspring and the next generation has a larger percentage of that trait. Microevolution change in allele frequencies in a population over generations Caused three main mechanisms: 1. Natural selection 2. Genetic drift change events that alter allele frequency 3. Genes flow transfer of alleles between populations Genetic Variation and Evolution Variation in heritable traits was a prerequisite for evolution Darwin did not know the mechanism to explain this though Genetic Variation Differences among individuals in the composition of their genes of other DNA segments Examples: facial features, height, voice, blood type Genotype variation, because phenotype can be altered the environment and personal actions Example: body builders Only the genetically determined part of phenotypic variation can have evolutionary consequences WITHOUT GENETIC VARIATION, EVOLUTION COULD NOT OCCUR Variation Within a Population Discrete Characters determined single gene locus with different alleles that produce distinct phenotypes Example: pea plants Qualitative Characters variation on a continuum within a population Result from the influence of two or more genes on a single phenotypic character Measure genetic variation: At whole gene level: Gene Variability Quantified as the average heterozygosity (average percentage of loci that are heterozygous) for fruit small percentage, but provides enough material for natural selection to work
Biology - notes
Course: General Biology I (BIOL101 )
University: Harrisburg Area Community College
